Apparatus for grinding a drill



,HRG HAMA' 2 Sheets-Sheet 1 March 1, 1960 APPARATUS FOR GRINDING A DRILL Filed Feb. 7. 1956 March l, 1960 JlRo HAMAI APPARATUS FoP` GRINDINGA DRILL Filed Feb. 7, 1956 f INVENToR.

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United States A APPARATUS FOR GRINDING A DRILL Jiro Hamai, Shinagawa-k, Tokyo-to, Japan Application February 7, 1956, 4sensi 10,564,065

4 Claims. t (Cl. 51h-72) This invention relates to apparatus for grinding twist".

drills and more particularly to an apparatus wherein the grinding of the point of a drill for the purpose of thinning the point, i. e. for the purpose of reducing'the width of the chisel edge or web is facilitated. `It is well known that the operation of properly sharpening a twist drill, if carried out by an operator holding the drill only in his hands, requires great skill if improper forming of the various .critical angles 'and dimensions required in the point' area is to be avoided; f

'It is "therefore a main object of this invention to provide for an apparatus for grinding twist drills in which the drill-is mechanically supported during the grinding ,rear surface 2a the circumferentialv edge of said wheel.

The inclination of the beveled grinding surface 2 against said axis corresponds to that of the edge 4 of the drill 3 against its axis. The gears 6, 7, 8 and 9 are provided for driving the wheel 1. The drive shaft 10 of the last gear 9 carries a crank 11. A motor may be used in lieu of the crank. A flat movable support member 12 .isf mounted turnable about the center line of pivot points 16:-,y and 16 supporting the axle 15 of the support member .12.

In all positions of the turnable support member 12 one. face thereof remains in close proximity and parallel with the flatrear surface 2a of the grinding wheel 1. The

movement of the upper end of the supporting member 12 t n direction of arrow Z is counteracted by a spring 13 attached to the lower end ofthe member 12 and to a member of the base 19. A stop pin 14 limits this movement. The brackets 17 and 18 mounted on the base 19 carry the above mentioned components of the apparatus. and are both inclined in the same direction.

In operating the apparatus, the crank 1'1 is rotated so 'aseto put the gear wheels 9, 8, 7 and 6 in motion and t o ""thus rotate the grinding wheel 1.

During such rotation of the grinding wheel, the drill edge 4 may be ground by bringing the same into contact with the beveled grinding surface 2 whereby the l drill edge 4 is ground at the proper clearance angle if operation, and particularly during that operation which.l

isldesigned to thin'the, point.

lWith above object in view, the apparatus according to the invention mainly consists, in combination,"of a rotary grinding wheel having a rim with a llat circular surface and a beveled surface, said surfacesv forming a circular edge; a basecarrying said grinding wheel Vfor rotation arounda fixed axis; a turnable support member having an edge portion and being mounted inl said. base for turning movement in a planeperpendicular to said axis and in close proximity to'said flat circular surffaceof said grinding wheel from a position in which said edge portion projects beyond said circularedge of said grindingwheel at least `to a position in which a point of saidv edge portion substantially coincides with said circularedge of said grinding wheel; and spring means i'nterposed be? tween said b ase and saidl turnable support jmemberjfor resiliently counteracting said'movement o f said tumable support member towards said axis, `so that a twist fdrill heldagainst the edge of thel grinding wheel is resiliently `I supported by said edge portion of said moyablesupport. member engaging a ank of a flute of the drill near the tip thereof.

The novel features which are considered as charactert FigQl is a front view of an apparatus according to the:

invention;

Fig. 2 is a side view, partlyin section, thereof, the section being taken along line B-B of Fig. 1;

Figs. 3 and 4 are cross-sectional fragmentary plan views along line A-A of Fig. l, the former showing the drill as seen in axial direction thereof, and the latter showing the drill in side view in the position for grinding its cutting edges; and v Figs. 5, 6 and 6a illustrate various phases of the grinding operation for'thinning the point.

Referring to the drawing, 1 is a grinding wheel mounted on a shaft 5 for rotation about the axis thereof and 2 is the beveled grinding surface forming together with a flat Harrow Z then the position shown in Fig. 6a will bey -than the thickness of the web carry out this operation, the end portion of the drill 3 f 'supported on a member 4a (Fig. 2) o r held horizontally,.. and accordingly the wheel 1 automatically:-y l e In this grinding 'opera-.v non not `only the cutting edgesl of the drill 3 'are sharp?" ened but also the chisel edge 20 In many cases it is desirable to thin the drill` point Y which means to give the width of the chisel'edge, i.e.v`

the inclination of the brackets 17 and 18 of the axis of the shaft 5 of determining lthe clearance angle.

is formed.

the outermost end portion of the web between the oppo site flutes of the drill, a suitable dimension which is less at that point.

is held with the llank 3a of one flute near the tip of the drill against the outer surface of the support member 12 ,t as is shown in Figs. 3 and 5 while the particular portion,

of the support member k12 is in the position shown in Figs. 1 and 4 where that will move together with member 12 into a position as:

illustrated vin Fig.V 3 in which the outer edge portion of .themember 12 substantially coincides with the cutting lt is clear that until then the wheel was prevented from touching and cutting the drill.' If

edge of the wheel 1.

no w further pressure is applied to the drill3 so that it movestogether with member 12 further in direction of reached so that the cutting edge of the wheel 1 will grind a notch into the web of the drill so as toreduce the Width of the chisel edge 20 to the'extent desired,

depending upon to what extent the last mentioned movement is continued.

Some types of twist drills are produced with a webwhich gradually increases from the tip towards the shank estantes Mar. 1., teso.

In order to A particular edge portion of merrber 12- somewhat projects beyond the cutting edg'eof the wheell 1;" If now some pressure'is exerted on the`drill 43 so-as to move the engaged edge portion of the member* 12, against the action of spring 13, in the direction' ofi,- arrow Z, then thedrill 3 steadied by the member 12; l

.rfi apanage..

edge portion 3' has been produced in the manner illustrated by Fig. 6a, the drill can be moved freehand so that the material between the curves 3' and 3 is removed. Also in this case the member 12 will preventany Without further analysis, the foregoing. will so fully reveal-'the gist of Vthe present invention thatothvers canA byrapplying curent knowledge readily adapt it for various( K n applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this inventionj and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

lWhat is claimed as new and desired to be secured byV Letters Patent is:

l. ln an apparatus for grinding twist drills, -in combina'tion, a rotary grinding wheel having a rim with a. tial;v circular surface and a beveled surface forming a circularv edge; a base carrying saidY grindinggwhe'elV for.

rotation arounda fixed` axis; a turnable support member y having an edge portion and beingmounted in .said base` for' turning. movement in a plane perpendicular to said.

axis` and 'in close proximity to said llat circular surface of saidgrinding ,wheel from a position in which said edge portion projects beyond said circular` edge of. sald grinding-.wheel to aposition in which a point `of said edge.: portionV coincides with said circular edge of said grindingwheel; and. spring means interposed betweensaid base` and said turnable support member for resilientlyv counteractingrsaidmovernent of said turnable support memberA towards said axis so that a twist drilly held against the edge of the grinding wheel is resiliently supported by said .edge portion of said movable support member engaging aiiank of a flute of the drill near the tip thereof.

2'. Inv anrapparratus for grinding twist drills, in corn-- biuation, azvrotary. grinding wheelV havinggawrim with a. atfcircular' surface and a beveled surface fcirmingaa. circular edge; a base carryingl said lgrinding wheel. for

rotation. arounda fixed axis; a turnable support member '.50

having a beveled edge portion and being mounted in sagd`bas`e for turning movement inra plane perpendicular 4. grinding a web portion at the point of the drill is resiliently supported by said beveled edge portion of said movable support member engaging a ank of a ute of the drill near`the tip thereof. v

3. In an apparatus for grinding twist drills, in combination, a rotary grinding wheel having a rim with a flat circular surface and a beveled surface forming a circular edge; a base carrying said grinding wheel for rotation around a tixed axis; a turnable support member having an edge portion and being mounted in said base for turning movement.V in a plane perpendicular to said axis and in. close proximity to said flat circular surface of said grinding wheel from a position in which saidv edge portion projects beyond said' circular edge of said grinding wheel to a position in which a point of said edge portion coincides with-said circular edge of said grinding wheel, said edge portion having a at surface on the side facing saidtlat surface of said grinding wheel and having on the other side a bevel surface extending at a selectedn angle to said liat surface thereof; and spring wheel for-grinding the web portion at the point of they drillv is resiliently supported by said bevel surface of. said' edge portion of saidY movable support member` v engaging a Vflank of a Vflute of the drill in contact with binatiom; al rotary grinding wheelhaving a rim witha. flat circular surface and a beveled `surfacefori'ningi ai. g cireularedge;v a base carrying said grinding wheel lforV rotationjaround a fixed' axis; an elongated supportN tos'aid axis andin close proximity to-said`at circulanA surface ofsaid grinding wheel from a position in .which said' bevelededge portion projects beyond'said circular` edge of said grinding wheel to a position in which a point offlsaid edge portion coincides with said circular edge of said grinding wheel; and spring means interposed' between `tle said base and said turnable support member.v

for resiliently counteracting said movement .of said turnablesupport member towards said axis so. that a twist.

drillfheldaganst the edge of the grindingzwheel; forsoneicutting, edge near the tip thereof.

4. In anapparatus for grinding twist drillsv in commember having an edge portion and being mountedv in said"` base for turning movement about a pivot point intermediate lits-ends ,in a plane perpendicular to said axis and in close' proximity to said flat circular Surface. offsaid "grinding wheel from a position in which said edge portion projects beyond said circular edge of said grind' ing wheel to a position in which a point of said edge portion coincides with said circular edge of said grinding wheel; pivot means in said base for turnably supporting. said support member at said pivot point; and springv means vinterposed between said baseand a point of said turnable'lsupport member `spaced Afrom. said pivot point*` opposite;top saidfedge portion for resiliently counter@ actingsaidmiovement' of`said turnable support membertowards -saidgaxisso that a twist drill held against the edge of'the grinding wheel for grinding the web portion..

at .the point of 4theid'rill is resiliently supported byglsaid.

edge". portionof'said movable ysupport member engaging` a tianlc'r` of a flute ofthe drill near the tip thereof.v

References Citedin the tile 0f this patent UNITED STATES PATENTS 

